On Mon, 25 Nov 2024, Richard Biener wrote:
> > The full `-msafe-bwa' feature is required for a fix, as the data race
> > comes from *outside* rather than from any lack of atomicity of the store
> > to the object itself. As the previous value of the object itself is
> > discarded, a plain RMW
On Mon, 25 Nov 2024, Maciej W. Rozycki wrote:
> On Sat, 23 Nov 2024, Maciej W. Rozycki wrote:
>
> > I found no previous bug report, so this is now PR target/117759[1]. An
> > obvious bug fix has been posted for review as well[2].
>
> I gave this issue some thought as I travelled across Europ
On Sat, 23 Nov 2024, Maciej W. Rozycki wrote:
> I found no previous bug report, so this is now PR target/117759[1]. An
> obvious bug fix has been posted for review as well[2].
I gave this issue some thought as I travelled across Europe over the
weekend and I have now withdrawn the proposed f
Hi Maciej,
On Sat, 2024-11-23 at 12:28 +, Maciej W. Rozycki wrote:
> > Thanks a lot for your work, much appreciated!
>
> You are welcome!
>
> > I gave this a try on gcc.git master with LRA enabled for both non-BWX and
> > BWX targets. BWX targets build fine with almost all languages enabled
Hi Adrian,
> > This has come out of a discussion[1] around the removal of non-BWX Alpha
> > support from the Linux kernel due to data races affecting RCU algorithms.
> > (...)
> > Comments, questions, voices of concern or appreciation, all very welcome.
>
> Thanks a lot for your work, much ap
On Tue, 19 Nov 2024, Maciej W. Rozycki wrote:
> > time I think the RMW sequence on _Atomic variables is a clear
> > bug that you'd need to fix also for -mno-safe-bwa.
>
> That's weird indeed, GCC internals manual clearly says:
>
> "'atomic_storeMODE'
> This pattern implements an atomic sto
Hi Maciej
On Mon, 2024-11-18 at 02:59 +, Maciej W. Rozycki wrote:
> This has come out of a discussion[1] around the removal of non-BWX Alpha
> support from the Linux kernel due to data races affecting RCU algorithms.
> (...)
> Comments, questions, voices of concern or appreciation, all ver
On Mon, 18 Nov 2024, Arnd Bergmann wrote:
> >> a) storing an '_Atomic' variable smaller than 8 bytes on non-bwx
> >>targets should use ll/sc, but uses a plain rmw cycle.
> >
> > I think there should be no problem with aligned 4-byte (longword) data
> > quantities, given that there are both pl
On Mon, 18 Nov 2024, Arnd Bergmann wrote:
> > This patch series addresses these issues in the last two changes, having
> > made generic test suite updates to improve coverage in the concerned area
> > first and then having addressed a bunch of issues in the code affected I
> > discovered in th
On Mon, Nov 18, 2024, at 13:22, Maciej W. Rozycki wrote:
> On Mon, 18 Nov 2024, Arnd Bergmann wrote:
>
>> > This patch series addresses these issues in the last two changes, having
>> > made generic test suite updates to improve coverage in the concerned area
>> > first and then having addressed
On Mon, Nov 18, 2024, at 03:59, Maciej W. Rozycki wrote:
>
> to zero a 9-byte member at the byte offset of 1 of a quadword-aligned
> struct, happily clobbering a 1-byte member at the beginning of said struct
> if there is a concurrent or parallel write to that member in the middle of
> the unpro
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